Such a sensor is suitable for example as an angle sensor for the control of brushless electric motors which have a stator Comprising several coils. The rotor of the electric motor has a permanent magnet which combines with the sensor to produce an angle of rotation dependent signal for the phase compatible control of the coils. Such an arrangement is known from the European patent application EP 954 085. A vertical Hall-effect element with several arms serves as the sensor whereby a Hall voltage dependent on the rotational position of the permanent magnet is produced in each arm. The Hall voltages are used to control the coils of the electric motor. The vertical Hall-effect element is sensitive to the components of the magnetic field produced by the permanent magnet which run parallel to the surface of the chip. It has the disadvantage that it can not be realised together with the processing electronics on the same chip because it is based on a special semiconductor technology.
The use of horizontal Hall-effect elements is also known which are sensitive to the components of the magnetic field produced by the permanent magnet which impinge vertically on the surface of the chip. These Hall-effect elements can be integrated into the processing electronics on the same chip. However, this solution has the inherent disadvantage that the Hall-effect elements must be arranged in the area of the edge of the permanent magnet where the vertical component of the magnetic field is largest. In the area of the rotary axis the vertical component is small. Placing of the Hall-effect element is dependent on the dimensions of the permanent magnet. With larger permanent magnets it is then no longer economic to integrate the Hall-effect elements onto one single semiconductor chip.
An angle sensor with a magnetic field sensor element which is based on the magnetoresistive effect is known from the patent U.S. Pat. No. 6,064,197. In order to increase the measurable angle range to over 180xc2x0, there is an additional Hall-effect element. However, the Hall-effect element must be positioned in a different location to the magnetic field sensor element as the magnetic field sensor element must measure the horizontally running components of the magnetic field of the rotating permanent magnet while the Hall-effect element must measure the vertical components of the magnetic field. In addition, sensors based on the magnetoresistive effect show hysteresis effects which limit the resolution.
Magnetic field sensors are known from the U.S. patent U.S. Pat. No. 5,942,895 and U.S. Pat. No. 6,184,679 which are sensitive to magnetic fields aligned parallel to the surface of the chip and which can be realised together with the electronics on a semiconductor chip. With such a magnetic field sensor however, only one single component of the magnetic field can be measured.
The object of the invention is to suggest a sensor which no longer has the disadvantages mentioned at the beginning.
According to a first aspect of the invention a sensor for the detection of the direction of a magnetic field comprises one single magnetic field concentrator with a flat shape and at least a first Hall-effect element and a second Hall-effect element or at least a first group and a second group of Hall-effect elements, whereby the Hall-effect elements are arranged in the area of the edge of the magnetic field concentrator.
The flat shaped magnetic field concentrator has the task to influence an external magnetic field in such a way that it penetrates the Hall-effect elements in an optimal way.
The Hall-effect elements can be so-called horizontal Hall-effect elements or so-called vertical Hall-effect elements. A horizontal Hall-effect element is sensitive to the component of the magnetic field which impinges vertically on its surface, while a vertical Hall-effect element is sensitive to a component of the magnetic field which runs parallel to its surface. For this reason horizontal Hall-effect elements must be placed below the magnetic field concentrator, vertical Hall-effect elements must be placed in the area beside the edge, outside of the magnetic field concentrator.
According to another aspect of the invention a sensor for the detection of the direction of a magnetic field comprises at least three magnetic field concentrators arranged symmetrically in a plane in relation to a point of symmetry which have, in the area of the point of symmetry, edges facing each other which run parallel to each other, and one Hall-effect element or one group of Hall-effect elements per magnetic field concentrator, whereby the Hall-effect elements are arranged in the area of the parallel running edge of the respective magnetic field concentrator.
In the following, embodiments of the invention are explained in more detail based on the drawing.